Re: Advice Needed re : Calibration of Tritium Stack Monitor

[slaback@micf.nist.gov]

The Canadian folks (Chalk River, CANDU facilities) have
published many papers on a variety of tritium sampling
procedures.

If you are dealing with oxide (tritiated water) a cold
trap and liquid scint analysis is the most sensitive
and cheapest technique.

For HT or DT gas and ion chamber is a good starting point,
but if you need to detect tabe 3 levels (ie. unrestricted
area concentrations) then either a flow thru proportional
counter or an oxidation process combined with collection
is needed.

Re: calibration...

If it is an ion chamber a one-time caibration combined with
an external source check should be adequate.

If it is an oxidation system then you need to assess collection
efficiency so that a full system cal is probably needed (but I
do not have direct experience with those systems so this is a
wild guess).

Regarding releasing material up the stack to do a calibration,
one can justify this on a one time basis to demonstrate in-situ
sampling efficiency, etc., but you should correlate this with
some other method so it is not needed routinely.  And even then
some licenses won't permit this without direct NRC approval.
If routine releases are being measured you should use a method
that utilizes these to obtain your calibration.

A little risk adds spice to life.
Lester.Slaback@NIST.gov